Dear L.,
If you can't get him to drink anything, then "wet" foods are your best options orally- just as you are doing. Double ear infections are really difficult. The Garlic ear drops great, when combined with mullein it helps with the pain as will Prescribed ear drops.
A lot of advice already given has mentioned drinking pedialyte- but since you can't him to drink that won't work yet. Also IVs have been mentioned. Consider giving him a pedialyte enema. His bowels will uptake the fluid and electrolytes and you may avoid an episode of IV therapy. Oil his rectum and insert a bulb syringe with room temperature pedialyte, gently put pressure on the bulb syringe and give him a small amount- 1/4 c to start with. Reintroduce more in about 30min-1 hour. See how that works. Yes, he may have diarrhea, but he should absorb what he needs. WATCH HIM CAREFULLY- sunken eyes, general weakness- his skin "Tents"- when you pinch it gently it doesn't go back down immediately. Those are signs of dehydration and of course, if you see those or are just concerned take him into the hospital right away. It is difficult to get an IV into anyone that is dehydrated- so don't wait until you see those signs.
As far as the ear infections: take him off any milk products beside breast milk, i.e. no milk or cheeses- however, he will need really good yogurt or acidophilus supplements to reestablish his intestinal flora due to the antibiotics as soon as he begins to eat again. (When he gets better, lessen his sugar intake, only naturally sweet foods.)
Massage under the ears and down with oil as was mentioned- I also use a small, warm rice pack held on the side of the neck under the ear and down the side of the neck where his eustacian tubes are. (Always check on your own neck for the correct temperature- your hands can tolerate more heat than other parts of your body!) In addition, Chiropractic care is wonderful for children with ear issues.
I use echinacea for short periods of time to boost immunities. You will be able to find a combination that is designed for children with ear problems in a glycerin base that will help at the Health food Store. (Glycerin tastes sweet)
I really understand about babies with ear problems! I have had three boys with very serious ear problems. After you get through this watch for "triggers", I mentioned milk products, sugar intake. Also watch how you bath him and see if you can completely avoid getting water in his ears. I found that teething sometimes would bring on more nasal discharge and ear problems- a good time to do the ear massage before it becomes an infeciton.
Be sure that you don't lay him down while nursing. Try to keep his head up at an angle (holding him in your arms) so that the milk drains down his throat and it doesn't remain in his mouth. He will like to nurse, it is probably very soothing!
I wish you the best!
H. B. MOM (mother of many-9)