This is the 16759th most frequent Russian word.
сливками
"Сливками" means "with cream" or "cream" in the instrumental plural form in Russian.
In this sentence, 'сливками' is used in an instrumental case, indicating the means by which something is achieved or done.
Напиток стал вкуснее благодаря добавлению сливками.
The drink became tastier thanks to the addition of cream.
Here, 'сливками' is again in the instrumental case, describing the material used for decoration.
Торт был украшен свежими сливками.
The cake was decorated with fresh cream.
In this usage, 'сливками' symbolizes a luxurious or indulgent pleasure, applied metaphorically.