My puppy ate fine for the first 2 days when we got her but she`s not eaten for nearly 3 days now tried every thing I can think of dried food puppy meat frozen beef weetabix rice pudding toast scrambled egg even fed her by syringe. Having to give her water by syringe gave her 10ml weetabix but sick after an hour and she`s got diahria sleeping loads but playfull when awake. She hasn`t had her jabs yet but she has been wormed

How old is the pup?

Has there been any vomiting or just refusing to eat?

Unfortunately we cannot diagnose on this site, only give you an idea as to what might be wrong but in this case there are too many variables to even guess.

Giving her small amounts of water with a syringe is great, it will keep her fluids up, just give her a syringe full every half hour or so.
But ultimately I would be calling a vet and booking an appointment.