One of the unique features of European XFEL is the high repetition rate of the X-ray pulses. Intra-train repetition rates of up to 4.5 MHz challenge the sample injection systems. The Sample Environment & Characterization (SEC) group of the EuXFEL develops sample delivery systems for all scientific instruments and provides user support in sample preparation, characterization, and delivery. One branch of SEC is dedicated to injecting liquid samples, especially using nozzles fabricated with submicrometer precision 3D printers. Cylindrical microjets are Soft X-ray liquid spectroscopy's most commonly used sample injection systems, however, suffering from several drawbacks. Their curved surface, for example, complicates determining the path length of X-rays in the sample. Here we present novel 3D-printed nozzle designs to produce microscopic flat sheet jets with micrometer thickness and high stability, intending to make this technology more widely available to users. A compact liquid jet setup at the MID instrument and an advanced characterization platform are also shown. The MID setup contains cooling capabilities to study phase transitions during droplet cooling and a recycling catcher system is used to limit the gas load and reduce sample consumption. The system is a prototype that can be transferred to other instruments.