South African lock Kruger, 30, has 17 caps for his country and previously played for Northampton and Bulls.
Australian-born but England-qualified Longbottom, 30, has been out with a long-term foot injury.
"He will fit perfectly into our plans and the pack we are building," said director of rugby Steve Diamond.
"I sourced Juandre when I headed up the recruitment at Northampton and he helped Saints to win silverware and also to the Heineken Cup final.
"We have some more signings to announce in the near future. We have been working hard on recruitment and our signings should do well in the Premiership and excite our supporters."
The pair add to Sale's already announced arrivals of hooker Rob Webber and back-row forward Laurence Pearce for next season.
Premiership club Sale Sharks have signed Racing Metro second row Juandre Kruger and Saracens tight-head prop Kieran Longbottom for next season.