The contaminated meat was discovered by a dog walker on the Cuckoo Trail in Hailsham on Wednesday.
The sausages, which had been sliced open and filled with the blue pellets, were handed in to police.
The RSPCA warned that dogs ingesting even small amounts of some substances could suffer kidney failure and die.
A spokesman said: "The RSPCA is deeply concerned about any spate of suspected poisonings, but especially one where evidence suggests it may be deliberate.
"Animals, and especially dogs, are often extremely curious and will be drawn to food.
"If anyone suspects that their dog has been poisoned they must take it to a vet immediately. If possible, they should take a sample of what the dog has eaten."
Poisoning is a criminal offence in the UK under the Animal Welfare Act 2006.
The maximum penalty for those found guilty is up to six months imprisonment and/or a fine of up to Â£20,000.
Cocktail sausages believed to have been stuffed with toxic slug pellets have been found at a popular dog-walking spot in East Sussex.