Not any specific sanction, just the US threatening that aid would have a significant effect. Egypt's defense budget is only around $5 billion.CAATSA doesn't apply to China. $1.3 billion might seem a lot but it is relatively less compared what it used to be thanks to inflation. $1.3 billion in the '80's is something different now.
That's why they haven't taken delivery of the Su-35, because they'll get slapped with CAATSA which would mean less support for the backbone of their airforce (F-16, E-2C) and army (M1, AH-64).