Taking antiretroviral treatment when you are living with HIV reduces the amount of HIV in your body. The less virus you have in your body, the less you will have in your semen, vaginal fluids or anal mucous. This means that you are less likely to pass on HIV during sex. If you adhere to your treatment and it’s working well, there may come a point where the amount of virus in your body is so little that normal tests will fail to detect it. This is what is called an ‘undetectable viral load’. It has often been classified as when the amount of HIV in your blood is below 50 copies/ml – according to a viral load test. If you have an undetectable viral load, you have eliminated HIV to such an extent that you can no longer pass it on through sex.
This was proven in 2016, in a study which included 548 mixed-status heterosexual couples. In all couples the positive partner was undetectable. No HIV transmission occurred across any of these couples despite there being thousands of instances of unprotected sex. To know whether you are undetectable you must have your viral load monitored. If you are adhering well to your treatment and aren’t having any problems then there is good reason to think that your viral load will be low. But you can't be sure that it is undetectable unless you have your viral load measured. Unfortunately, this means that people without access to viral load monitoring won't know for sure if they're undetectable.

To get HIV the sexual fluids from one person have to enter another. This doesn't happen with handjobs. If you are sharing a sex toy that's being inserted, the risk is minimal, but it's still advised that you wash the toy between use and use a new condom for each person. Although it's very unlikely that you would get HIV by sharing sex toys, it's easy to pass on other sexually transmitted infections (STIs) such as chlamydia and gonorrhoea this way. Following this advice will protect you from these.

Yes, menstrual blood and other sexual fluids can contain HIV. If you’re living with HIV, your viral load is likely to be higher while you’re on your period. This means you are more likely to pass on HIV during this time. If you’re HIV-negative, you can still get HIV if you have sex during your period. While you’re having a period, changes in your vagina make it easier for HIV to enter your body.
Using condoms, being on effective treatment and taking PrEP all minimise these risks.