How much money per year am I allowed to give my sister without penalties and taxes.

If your sister has a special needs trust (because she is receiving needs-based public benefits in the form of Supplemental Security Income), and it is established with NONE of her own money, you can contribute any amount to it.  You can also contribute up to $15,000 per year to an ABLE account (www.stable.org). However, if your sister has some other sort of trust and is receiving not Supplemental Security Income ($794/month in 2021) and Medicaid but Social Security Disability Income (in excess of the SSI figure), you are only limited by the Internal Revenue Code.  This allows anyone to give anyone else up to $15,000/year without paying gift tax or $70,000, filing a Form 709 with their 1040 to explain that it is intended to be a gift over five years.