I know someone really good here (I cant remember their name, sorry!) reccomended soaking lettuice in water before giving it to your piggies first because that means they're getting more fluids.
Of course, some people say that you shouldnt give lettuice to guinea pigs, which confuses me as mine have allways loved it and never had a problem.
HOWEVER, I know they really can have Kale, and you can get that whole, or prepackaged and sliced allready. Again, you could soak that in water first to ensure your pig gets more fluids!
?do be carefull about oranges.. If as you said you've got to let him eat whatever he will eat then great, just be carefull of mouth sores.
Melon, as someone else suggested, is good too. Avoid giving them the seeds. Honeydew is a bit sweeter, so depending on the pig, this might be better or worse than the big green mellons you can get.
Recently I've been trying to give my pigs a wider variety of fruit and veg, thus far I've found that avocados and mangoes are quite favoured by the guinea pig community.. But do remember that avocados are quite fatty.
If the sitaution is getting desperate, you might want to try tinned spinnach? I dont think tinned stuff is so good for them as alot of the nutrients have been taken out, but if the situation is drastic then that might be atleast something your guinea pig could eat.
Oh yes,
dont try baby food! I allways thought that baby food would help, but someone here told me that it can actually give a guinea pig bloat and hurt them and make them even sicker, so please
dont try that !(unless your vet specifically reccomends it..)
This sounds weird, but have you tried peeling grapes for your pig? sometimes the hard dry skin can put them off eating grapes, but they show more interest if you take the time to peel the grape. They're another juicy super wet fruit.
Good luck.. sorry I couldnt be of any real help
